Disposers don't last forever. The one at my old house "appeared" and "sounded like" it was grinding up food... and it was. Sort of. But it was not grinding it up enough to be washed away, and it accumulated about 50' away in the pipes running thru the basement ceiling. It took two plumber's visits to diagnose this, AND a new disposer.... So if your's is more than say 10 years old, I'd spring for a new one, which is cheaper than 2 plumbers visits, esp if you can install it yourself.